Personally, I use it because it allows me to organize my code into separate files, which makes it easier to scale and maintain the code. In order to use Rollup we must install it globally.
Remember to use sudo. This allows you to access Rollup commands in whatever project you work with. In addition, create index. Keep in mind, the bundle. We will talk about this later. Make sure that the input and output source path is correct with your folder structure, and that this file is placed in the main folder.
We are almost ready, but first we need to link to the right source file in our HTML template. This will load the ES5 file which is compiled from ES6. In order to verify that the Rollup command works, we need to setup a simple OOP structure.
We will create a car. Keep in mind that this file exports a new instance of the car. This chapter gives tips. The following are a few important npm packages. All Babel packages reside in a single repository on GitHub. Browsing their source code and their package.
The configuration data is an object of JSON data that is assembled from various sources which are described later. Two configuration options have much influence on how the output is produced: plugins and presets. These are explained next. The remaining configuration options are explained in the Babel documentation.
Roughly, plugins are functions that are applied to the input during compilation. Two important categories of plugins are:. However, each transform plugin that depends on a syntax plugin automatically activates that plugin. Plugins are installed via npm. Their package names are their names plus the prefix babel-plugin- :. You can specify:. Presets are installed via npm.
Their package names are their names plus the prefix babel-preset-. For example, this is how to install the preset es :. The main source of configuration data is a file. Babel first looks for. The contents of. For example:.
Each npm package has a file package. Babel allows you to use that file for configuration, as an alternative to. Then it must have a property babel otherwise Babel ignores package. The value of that property is an object with configuration data.
Babel searches for package. If there is both a. If you are using babel-node , you can specify the following options and a few others via the command line:.
The following command runs my-script. As you can see, babel-loader supports the property query for specifying Babel options. This chapter explains how to configure how Babel 6 accesses its own helper functions and the ES6 standard library. There are two ways of fulfilling these dependencies: by installing functionality globally or via modules. In both cases the functionality is delivered as npm packages. The following npm packages install their functionality globally and let you access it via global variables:.
The code generated by Babel usually has two kinds of external dependencies that need to be fulfilled. First, most code invokes functionality of the ES6 standard library. By default, you access this functionality via global variables:.
Second, Babel has helper functions e. By default, the code of helper functions is inlined , inserted into each file. There are two ways in which you can get the standard library and non-inlined helpers: via global variables and via module imports.
How is explained in the next sections. The plugin ensures that all helpers are invoked via methods of the global object babelHelpers. If you transpile it with the es preset and without external-helpers , you get:. How do you install the object with the helpers into the global variable babelHelpers? Via a file generated by the command line tool babel-external-helpers.
The tool is part of the npm package babel-cli. The file is available in three formats:. The package babel-polyfill contains a module that installs several things into global variables:. The polyfills are provided by core-js , which you can see if you look at the two import statements making up this module :. Install babel-polyfill via npm as a runtime dependency if you find that any of the aforementioned functionality is missing in your transpiled code.
In current Node. The module will check global variables and only install missing functionality. The downside of the polyfill is that you always deliver and load all of the functionality, independently of how much you use. The import statement needs to happen before you access the runtime library. It installs the polyfills globally. The next two sections explore how transform-runtime works for helpers and for the standard library.
Note that each function sits in its own module, which ensures that only functions you actually use end up in bundled code. The plugin transform-runtime handles helpers automatically, but for much of the standard library, extra work is required. Take, for example, the following ES6 code:. However, transform-runtime does not detect method calls like those in the following ES6 code:. There are no imports — the input code in basically untouched. However, the second method call is direct and ignored, too.
You can use them to replace method calls such as this one:. You can look up how transform-runtime maps identifiers and chained property accesses to core-js modules in the repository file definitions. This is an excerpt:. That means that transform-runtime provides Set , Array.
Given that transform-runtime requires you to access properties of built-in constructors if you want to make a method call, using core-js directly is a useful alternative to that plugin. Another way of accessing standard library functionality non-globally is to import entities individually:. For libraries, you must not touch global variables, which is why everything must come from imports:.
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